New antiserum against Ki-67 antigen suitable for double immunostaining of paraffin wax sections.

Aims: To prepare a rabbit antiserum equivalent to MIB 1 to permit the simultaneous assessment of cell proliferation and other markers of interest using double labelling studies.

Methods: Rabbits were immunised with a synthetic peptide deduced from the cDNA sequence coding for the Ki-67 antigen. Serum samples were tested for immunoreactivity using different immunobiochemical methods.

Results: A polyclonal antiserum was derived which detects the native as well as recombinant parts of the Ki-67 antigen in different test systems. Furthermore, the antiserum stains the Ki-67 antigen in routinely processed, paraffin wax embedded material.

Conclusions: After antigen unmasking by microwave treatment the antiserum described here represents a powerful tool for the determination of growth fractions even in archival material. It is especially suitable for double staining experiments in combination with monoclonal antibodies.